Heat treating apparatus



Sept. 27, 1960 T. c. PEW

HEAT TREATING APPARATUS Filed Aug..8, 1.957

M Hu m 1 J-....H|H|HH,. I I j m a 6 GMA/YMU J/ A u a f K A v W a A a M pa Q X 9 b VEJMTOM Thom pew z 4} .414., 41% Cflww-ome United States Patent HEAT TREATING APPARATUS Thomas C. Pew, Sterling Commercial Steel Ball Corp., Sterling, Ill.

Filed Aug. 8, 1957, set. No. 676,998

1 Claim. 01. 110-173 This invention relates to a heat treating furnace of the type which is lined with a heat resistant material and, more particularly, to a furnace in which the workpieces are loaded in the heating chamber through an elongated opening formed by a continuation of the lining. In such furnaces, the opening is closed by a disk which seats against a flange integral with the lining and extending around the opening near the inner end thereof. The outer end portion of the opening is closed by an insulated plug and a shaft is threaded through the plug and connected to the disk so that the disk is moved into engagement with the flange by turning the shaft.

The general object of the invention is to provide, in a heat treating furnace of the above character, a new and improved plug assembly which closes the heating chamber more effectively as compared to prior arrangements, which reduces the possibility of damage to the lining and which is relatively inexpensive to repair.

The principal object is to achieve the foregoing by forming the disk separately with the shaft simply abutting the disk and by making the disk comparatively thin so that it bows readily and without producing forcw great enough to break the flange away from the lining.

Other objects and advantages of the invention will become apparent from the fol-lowing detailed description taken in connection with the accompanying drawings, in which Figure 1 is a fragmentary longitudinal sectional view of a heat treating furnace embodying the novel plug assembly of the present invention.

Fig. 2 is a perspective View of the disk.

Fig. 3 is a fragmentary sectional view of the flange, the disk and the shaft.

For purposes of illustration, the invention is shown in the drawings embodied in a furnace for heat treating metal parts such as small steel balls used in bearings. The furnace comprises an insulated cylindrical housing 5 enclosing a chamber 6 where the workpieces are heat treated. The chamber is heated by any well-known means (not shown) and is loaded through an elongated cylindrical opening 7 in one end of the furnace. The heating chamber is lined with a cylinder 8 of heat resistant material such as a high temperature alloy of nickel and chromium and the cylinder extends through one end of the housing and defines the opening 7. The latter is closed during the heating period by a plug assembly 9.

Herein, the plug assembly includes a hollow cylinder 10 adapted to fit into the opening 7 of the furnace and forming an annular compartment 11 filled with an insulating material 12. A circular capping plate 13 bored at its center is bolted to the open end of the cylinder 10 to close the compartment 11. The size of the capping plate 13 is such that it overlaps the opening 7 to form a flange 14 abutting against the end of the lining 8. A plurality of clamps around the periphery of the capping plate 13 have hooks 15 which catch on a projection 15' rigid with the outer lip of the cylinder 8 and secure the plug assembly 9 in the opening 7.

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A shaft 16 with a hand wheel 17 at the outer end, a threaded portion 18, and an enlarged portion 19 at the inner end, is projected through a boss 20* integral with the capping plate 13. A nut 21 welded to the outer end of boss 20 engages the threaded portion 18 of the shaft 16 to provide a means for advancing the shaft through the plug assembly 9. The enlarged portion 19 of the shaft fits snugly with the internal bore of the cylinder 10 to guide the shaft into the opening 7 and at the inner end of the shaft is a disk 22 seated on a peripheral flange 23 integral with and extending inwardly from the internal lining 8 of the furnace.

In accordance with the present invention, the disk 22 and the shaft 16 are constructed and arranged to cooperate in a novel manner whereby the disk effectively closes the heating chamber 6 even upon elongation of the shaft as the latter is heated and this without the danger of the flange 23 breaking away from the lining 8. Moreover, as compared to prior arrangements, the service life of the disk is increased substantially and the disk may be replaced inexpensively. To these ends, the disk is formed separately and the shaft simply abuts against the central portion of the disk so that the disk may bow upon elongation of the shaft and still be seated against the flange. In addition, the disk is thin enough that it bows without producing stress% which are great enough to break the flange.

Herein, the inner end of the shaft 16 is tapered and projects into a hole 24 at the center portion of the disk when the latter is seated against the flange 23. The amount of taper of the inner end of the shaft 16 and the size of the hole 24 in the disk is correlated so that the tapered end portion 25 may partially enter the hole 24 and results in an abutting engagement between the disk and the conical surface of the tapered end portion of the shaft when the latter is advanced toward and against the disk.

In preparation to operating the furnace, the components are in the positions shown in Fig. 1 with the plug assembly inserted into the opening 7 of the furnace and clamped to the lining 8, the disk seated against the flange 23 and the shaft 16 advanced by the hand wheel 17 into abutment with the disk thus holding the disk securely against the flange 23. Because of the heat generated in the furnace, the shaft 16 will elongate due to thermal expansion thus creating an axial force on the disk 22. The disk is made relatively thin so that it will bow readily under this force as shown in broken lines in Fig. 1. The thickness of the disk is correlated with the strength of the flange 23 so that the disk bows upon elongation of the shaft without producing forces great enough to break the flange away from the lining 8. A thickness of about /2 inch has been found satisfactory in the average case. The coaction of the tapered end portion 25 of the shaft 16 with the disk 22 at the hole 24 insures the centering of the disk about the opening of the heat treating chamher to provide a positive covering for the heat treating chamber even while the disk is in a dished configuration.

During continued service use, the disk 22 becomes permanently bowed and the dishing becomes progressively greater. When the bowing becomes too great, the disk can be reversed as shown in Fig. 3 and, in this position, the thermal elongation of the shaft will force the disk to bow in the opposite direction. The disk can, therefore, be stressed in opposite directions many times before becoming fatigued to the point of failure. Moreover, it is a simple and inexpensive operation to replace the disk.

I claim as my invention:

A heat treating furnace having, in combination, a walled enclosure defining a heating chamber and having an elongated cylindrical opening communicating with said chamber, a lining of heat resistant material disposed within said chamber, an annular internal flange integral with said lining and extending around said opening adjacent the inner end thereof, a cylindrical insulating plug adapted to be inserted in the outer end portion of said opening and spaced outwardly from said flange, said cylindrical plug having an axial bore extending therethrough and including a nut rigid with said plug adjacent the outer end thereof and coaxial with said bore, means for clamping said plug to said enclosure, a thin metal disk seated against said flange and enclosing said chamber, and a shaft threaded through said nut and having a portion sliding in the inner end of said bore to maintain the shaft coaxial with said opening, said disk having a central hole formed therein and said shaft having a tapered inner end projecting partially into said hole whereby the shaft holds the disk against said flange and centered relative to the flange, the thickness of said disk being correlated to the strength of said flange whereby the disk bows upon thermal elongation of said shaft without breaking the flange.

References Cited in the file of this patent UNITED STATES PATENTS 168,390 Glachet Oct. 5, 1875 1,780,534 Peterson Nov. 4, 1930 1,924,437 Johnson Aug. 29, 1933 1,988,223 Voss Jan. 15, 1935 2,289,181 Dawson et a1 July 7, 1942 2,778,785 Otto Jan. 22, 1957 FOREIGN PATENTS 387,217 France May 1, 1908 

